With tightening environmental regulation in recent years, market needs for materials that do not contain harmful metals have been increased. For that reason, in the field of automobiles, the switching from a lead-tin alloy plated steel sheet, which has been a main ingredient of fuel tanks, to a material not containing lead has been promoted. Accordingly, to a unique required performance of the fuel tanks, which is high inner corrosion resistance with respect to an enclosed fuel is enclosed (hereinafter, also referred to as fuel corrosion resistance), many suggestions are given involving using zinc-based plated steel sheets instead of lead-tin-based plated steel sheets as inner and outer sheets of automobiles (for example, see the following Patent Literatures 1 to 3).
The technologies using zinc-based plated steel sheets described above each have an assumption that chromate treatment is performed, and therefore are incompatible with the recent market needs for not using harmful metals. For this reason, as described in the following Patent Literatures 4 to 9, a chromate-free zinc-based plated steel sheet that does not contain chromium for a fuel tank is disclosed.
Citation ListPatent LiteraturePatent Literature 1:JP H5-106058APatent Literature 2:JP H9-324279APatent Literature 3:JP H9-324281APatent Literature 4:JP 2004-169122APatent Literature 5:JP 2007-186745APatent Literature 6:JP 2013-133527APatent Literature 7:JP 2013-227646APatent Literature 8:JP 2011-38139APatent Literature 9:WO2007/011008